Well pump



Sept. i3, 1966 R. P. VINCENT 3,272,144

WELL PUMP Filed July 31, 1964 IIIIIIIIIII IIIIIIIIIIIIIIIHIIQIIII IImm:IIIIIIHHIHHI! IMIIIIHIIIII \IIIIIIIIIIIIIIIIIIIIIIII il? .Im-IIlifelllwll III/1. I I I I Il Iammmm I@ l @All IIIIIIIII! INVENTOR. RENIC P. VINCENT ATTORNEY United States Patent O 3,272,144 WELL PUMP Renic l. Vincent, Tulsa, Okla., assignor to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Filed July 31, 1964, Ser. No. 386,659 4 Claims. (Cl. 10S- 204) This invention relates to the lifting of fluids from a well, and more particularly, is concerned with a sucker rod pump for pumping corrosive or abrasive liquids.

Sucker rod pumps have been used for many years for lifting formation fluids from wells drilled into the earth. Basically, the well fluids are lifted from the well by means of a subsurface pump which is actuated from the surface by a sucker rod string connected to a walking beam. A suitable driver actuates the walking beam to raise and lower the sucker rod string in the well. The subsurface pump generally comprises a plunger connected to the lower end of the sucker rod string, a working barrel within which the plunger reciprocates, and travelling and standing valves for controlling the fluid flow into and out of the working barrel. A description of various types of sucker rod pumps may be found in the book Modern Oil Well Pumping by Joseph Zaba, published by the Petroleum Publishing Company, 1962.

Sucker rod pumps, mentioned above, have found widespread use in the oil industry and in other similar industries for lifting well fluids, and commercially available pumps of this type have proven satisfactory for general use. Recently, in situ combustion recovery methods have been developed for recovering oil from underground formations. In the practice of such recovery method, water is sometimes injected into the well, and the injected water and/ or formation water often dissolves combustion products so as to become acidic and very corrosive. In the pumping of such corrosive fluids, the combination of the corrosive effect of the fluid and the metal-to-metal wear of the pump parts presents severe maintenance problems. In some instances it has been found necessary to pull pumps employed in this type service at intervals of two or three days in order to repair either the bottomhole pump or the tubing and sucker rod string. Conventional methods of mitigating corrosion of the pumping equipment have been found unsatisfactory in that they are either ineffective or pumping costs are increased very considerably.

An object of the present invention is a well pump adapted for pumping corrosive and/or abrasive fluids, which pump is of simplified construction, while being durable and economical. Other objects of the invention will become apparent by reference to the following description of a preferred embodiment of the invention, given in connection with the accompanying drawings wherein:

FIGURE 1 schematically illustrates a sucker rod pump, according to the invention, employing a dual tube arrangement; and

FIGURE 2 schematically illustrates a sucker rod pump, according to the invention, employing a single tube arrangement.

Briefly, the present invention provides a reciprocating well pump employing a reservoir of a protective fluid, preferably an inhibited lubricating oil, on the power side of the pump plunger and means for maintaining the protective fluid in the reservoir at a pressure greater than the maximum fluid pressure occurring in the pump on the working side of the plunger during the pumping operation. A film of the protective fluid is maintained between the wall of the pump cylinder and the plunger as a result of the pressure differential between the fluid in ICC the protective fluid reservoir and the fluid being pumped, and the exposure of the moving pump parts to corrosive pumped fluids is minimized.

Preferably, the above-mentioned pressure differential is maintained in the protective fluid reservoir by a pressured gas reservoir connected to the protective fluid reservoir to provide a gas cushion for maintaining a substantially constant pressure on the protective fluid.

. Referring now to the drawings, wherein like numbers are employed to designate like elements shown in each of the figures, FIGURE l illustrates one embodiment of a sucker rod pump employing a solid sucker rod string in well tubing and a separate discharge tubing, while FIG- URE 2 illustrates the use of a hollow sucker rod string in well tubing. A well bore 11 is formed in the earth to a suitable depth, and the well bore may be cased or left open, as desired. A string of well tubing 12 is set in the well extending to a depth below the level of liquid 13 contained in the well, so that the pump cylinder, or barrel 14 is immersed in the liquid. Barrel 14 may constitute an extension of tubing 12 or may be a separate element connected to the well tubing. At the lower end of barrel 14 there is provided a standing check valve 16 which permits unidirectional flow of the well fluid into the pump barrel on the lower, or working, side of reciprocating plunger 17 positioned in the pump barrel. Sucker rod string 18 is secured to the upper, or power, end of plunger 17 and extends upwardly to the surface. Typically, the upper end of sucker rod string 18 is connected to a polished rod, passing through a stufllng box, attached to a bridle which is connected to the horsehead of a walking beam driven by a suitable power unit. The connections at the upper end of the sucker rod string and the power unit have not been shown in the drawings and need not be described in detail herein, since these elements are well known in the art and form no part of the present invention. lAs shown in FIGURE l, check valve 19 is positioned in outlet 21 of barrel 14 to permit unidirectional flow of fluid from the barrel into discharge tubing 22 connected to outlet 21. Discharge tubing 22 extends upwardly to the surface and may be connected to a storage tank or the like at its upper end.

The pump of FIGURE 2 employs a hollow sucker rod string having a longitudinal opening 18a extending through the string and communicating with longitudinal conduit 17a provided in the plunger. Travelling valve 23 is positioned in the plunger at the lower end of conduit 17a which forms the outlet for fluids discharged from the pump barrel. Valve 23 permits pumped fluids to flow from the pump valve in a unidirectional manner, and the pumped fluids are conveyed upwardly through conduit 18a to the surface for storage or other disposition.

The annular space 26 between .sucker rod 18 and the inner wall of tube 12 above plunger 17 provides a reservoir for protective fluid which as mentioned above may be any suitable noncorrosive and inert liquid, preferably a relatively light lubricating oil which may contain a suitable corrosion inhibiting agent selected from well known, commercially available corrosion inhibitors. Annular space 26 may be completely fllled with the protective fluid, or the level of the protective fluid contained in the reservoir may be maintained at a suitable level in the tubing. However, it is critical that the hydrostatic pressure of the protective fluid at the bottom of the vertical fluid column, i.e., on the top side of plunger 17, is always greater than the maximum fluid pressure in the Ibarrel below the working end of the plunger. For example, if the protective fluid has a density greater than the fluid being pumped and if the level of protective fluid in the tubing is as great as the level of fluid in the discharge conduit, the desired pressure differential will be maintained. However, if the density of the protective fluid is less than that of the fluid being pumped, it will be necessary to employ means for increasing the hydrostatic pressure at the lower end of the protective fluid column so as to achieve the desired pressure differential.

Typically, the vertical column of protective fluid in the reservoir extends tothe surface and, in order to assure that suflicient pressure exists at the bottom of the protective fluid column, a pressured gas reservoir 27 is provided in vessel 30 connected by conduit 28 to the upper end of tubing 12, with a preselected pressure being maintained in the gas reservoir, so that the pressured gas reservoir acts as a gas spring on the top lof the fluid column. Additionally, the lower portion of vessel 30 containing the gas reservoir may be employed as a liquid ysurge vessel for storing a suflicient quantity of protective fluid to automatically fill reservoir 24 as protective fluid is utilized in coating the plunger and pump barrel surfaces. Periodically, additional protective fluid may be added to the surge vessel to replace that used during the pumping operation.

If it is desired to use a corrosion inhibitor in the protective fluid, injection pump 31 may be employed to inject the corrosion inhibitor, `or a solution thereof, into the system via conduit 32 connected to conduit 28, or other suitable connections may be employed. The pump of the present invention is well adapted for the use of an inhibited protective fluid, since high concentrations of corrosion inhibitor may be maintained in the protective fluid and it is not necessary to inhibit large volumes of the corrosive pumped fluid as in conventional practice. Normally, relatively small volumes of protective fluid are utilized in protecting the moving parts of the pump from corrosion, the amount of fluid so utilized being governed by the clearance between the plunger and the inner wall of barrel 14 and by the pressure differential maintained -across the plunger. Sealing rings may or may not be used on the plunger, depending upon the design for each installation. Normally, sealing rings are not necessary and the clearance between the plunger and the wall of the pump barrel may be maintained at about 0.00'1 inch on a side.

Since annular space 26 is normally lled with protective fluid, no corrosion or undue wear occurs on either the sucker rod string or the tubing, as is the case in con- Ventional installations wherein corrosive fluids are being handled. Those parts of the above-described pump which are exposed to corrosive fluid, e.g., the plunger, travelling and standing valves, etc., may be fabricated from corrosion-resistant materials, and, if desired, the discharge conduit may be coated with a protective film on the side exposed to the pumped fluid.

From the foregoing description of a preferred embodiment of the invention various alterations and modifications in the details of construction may become apparent to one having ordinary skill in the art, and it is to be understood that such modifications and alterations fall within the spirit and scope of the appended claims.

I claim:

1. A reciprocating pump for pumping fluid from a well which comprises:

(a) a vertical first conduit suspended within said well;

(b) a pump cylinder connected to the lower end of said first conduit;

(c) a string of hollow sucker rods suspended within said first conduit;

(d) a plunger connected to said string of hollow sucker rods `and reciprocally mounted within said cylinder in sealing engagement with the interior surface of said pump cylinder,

said plunger having a second conduit therethrough and a check valve means in said second conduit permitting flow only from fbeneath said plunger upwardly through said second conduit, said second conduit being in fluid communication with the interior of said string of hollow sucker rods,

said plunger forming a barrier between said second conduit and a protective fluid reservoir formed above the plunger within said first con duit and exterior of said string of hollow sucker rods so as to prevent fluid communication bel tween the reservoir and the second conduit;

(e) an inlet means in said cylinder below said plunger communicating said cylinder with said well for admitting well fluid into said cylinder, said inlet means including a check valve means for unidirectional flow of fluid from the well into said cylinder;

(f) a column of protective fluid contained in the protective fluid reservoir formed in said first conduit exterior of said string of sucker rods and above said plunger, and

(g) means for maintaining the lower end of said colunie of protective fluid above said plunger at a pressure greater than the maximum fluid pressure in said cylinder below said plunger.

2. The apparatus of claim 1 further including a pressure gas reservoir fluidly connected to the interior of said conduit for maintaining said protective fluid at a preselected pressure.

3. The apparatus of claim 1 wherein said protective fluid is a lubricating oil.

4. The apparatus of claim 3 wherein said lubricating oil contains a corrosion inhibitor.

References Cited by the Examiner UNITED STATES PATENTS 1,376,877 5/1921 Herron 103-204 1,614,865 1/1927 Boden. 1,643,616 9/1927 Zinn et al. 103-44 1,737,248 11/ 1929 Kelley. 1,758,376 5/1930 Sawyer 103-204 3,098,452 7/1963 Davis 103-206 X ROBERT M. WALKER, Primary Examiner. 

1. A RECIPROCATING PUMP FOR PUMPING FLUID FROM A WELL WHICH COMPRISES: (A) A VERTICAL FIRST CONDUIT SUSPENDED WITHIN SAID WELL; (B) A PUMP CYLINDER CONNECTED TO THE LOWER END OF SAID FIRST CONDUIT; (C) A STRING OF HOLLOW SUCKER RODS SUSPENDED WITHIN SAID FIRST CONDUIT; (D) A PLUNGER CONNECTED TO SAID STRING OF HOLLOW SUCKER RODS AND RECIPROCALLY MOUNTED WITHIN SAID CYLINDER IN SEALING ENGAGEMENT WITH THE INTERIOR SURFACE OF SAID PUMP CYLINDER, SAID PLUNGER HAVING A SECOND CONDUIT THERETHROUGH AND A CHECK VALVE MEANS IN SAID SECOND CONDUIT PERMITTING FLOW ONLY FROM BENEATH SAID PLUNGER UPWARDLY THROUGH SAID SECOND CONDUIT, SAID SECOND CONDUIT BEING IN FLUID COMMUNICATION WITH THE INTERIOR OF SAID STRING OF HOLLOW SUCKER RODS, SAID PLUNGER FORMING A BARRIER BETWEEN SAID SECOND CONDUIT AND A PROTECTIVE FLUID RESERVOIR FORMED ABOVE THE PLUNGER WITHIN SAID FIRST CONDUIT AND EXTERIOR OF SAID STRING OF HOLLOW SUCKER RODS SO AS TO PREVENT FLUID COMMUNICATION BETWEEN THE RESERVOIR AND THE SECOND CONDUIT; (E) AN INLET MEANS IN SAID CYLINDER BELOW SAID PLUNGER COMMUNICATING SAID CYLINDER WITH SAID WELL FOR ADMITTING WELL FLUID INTO SAID CYLINDER, SAID INLET MEANS INCLUDING A CHECK VALVE MEANS FOR UNIDIRECTIONAL FLOW OF FLUID FROM THE WELL INTO SAID CYLINDER; (F) A COLUMN OF PROTECTIVE FLUID CONTAINED IN THE PROTECTIVE FLUID RESERVOIR FORMED IN SAID FIRST CONDUIT EXTERIOR OF SAID STRING OF SUCKER RODS AND ABOVE SAID PLUNGER, AND (G) MEANS FOR MAINTAINING THE LOWER END OF SAID COLUME OF PROTECTIVE FLUID ABOVE SAID PLUNGER AT A PRESSURE GREATER THAN THE MAXIMUM FLUID PRESSURE IN SAID CYLINDER BELOW SAID PLUNGER. 